i had the same problem, so i can help u =D
lets hope u have windows, open where u have moved the files from ur sd card to ur computer(the ISOs) clik tools>folder options the view tab and uncheck "Hide extensions for known file types". then rename ur ISOs IN ORDER U RECIEVED THEM to ____.iso.001 ___.iso.002 and so forth.
then use this software below, and use the joining tabhttp://www.jaist.ac.jp/~hoangle/filesj/FFSJ.exe
HOPE IT HELPS!